1. Field of the Invention
The present invention relates to a vacuum circuit breaker, which can enhance a current capacity.
2. Description of the Related Art
In a conventional vacuum circuit breaker, an upper main circuit conductor and a lower main circuit conductor are provided above and under a vacuum valve. The lower main circuit conductor is connected to a movable current-carrying rod of the vacuum valve via an extendable flexible conductor. Since the movable current-carrying rod of the vacuum valve is generally rod-shaped, a plate-like coupling conductor is connected to the movable current-carrying rod and one end of the flexible conductor is connected to the coupling conductor, while the other end thereof is connected to the lower main circuit conductor. A fixed current-carrying rod of the vacuum valve is fixed to the upper main circuit conductor by bolts (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2007-273383 (pages 3 and 4 and FIG. 1).
The conventional vacuum circuit breaker described above has the following problems.
As the current flowing therethrough increases, the electrical resistance in the main circuit components, such as the main circuit conductor, need be reduced. However, to reduce the electrical resistance, the sectional area of the main circuit components must be large, which causes an increase in size of the outer shape of the vacuum circuit breaker. Further, since the mass of the movable side inevitably increases, the operation energy to operate the movable side and the rigidity of the vacuum circuit breaker body need be increased.
The portion of the main circuit components that most increases the electrical resistance is the movable side, which includes a number of connecting parts. Therefore, it is required to reduce the number of parts of the movable main circuit components and suppress the electrical resistance.